The present invention is directed to an orbital applicator tool for use in combination with a robot to form a dispensing system in which a ribbon of material having a variable width and thickness can be applied to a work piece or substrate in a predetermined selectable and/or programmable pattern.
The automotive industry is increasingly using a wide variety of adhesives and sealants in the production of vehicles. For example, adhesives and sealants are used in the assembly of hem-flanged parts, such as doors, decks, and hoods. By way of example, sealing materials can be used independent of other mechanical means, or can be used in combination with more conventional connecting means, such as spot-welding techniques. In spot-welding techniques, the sealant is first applied and then the sheet metal is welded through the sealant. The combined sealant and spot-weld configuration allows the distance between spot-welds to be increased while reducing the number of welds required. Alternatively, welding is being eliminated by employing greater use of structural adhesives.
The use of sealants and adhesives in automated assembly can create problems if the material is improperly applied. For example, if the dispersal pattern extends beyond the end of the work piece, the work area can be subjected to over spray requiring cleaning. If excessive volume of material is applied in a hemming operation, the material can contaminate the paint primer base prior to painting. Excessive material can also contaminate hemming dies, and adversely impact the ability to paint over exposed adhesive or sealant that has been expelled from joints because of the application of excessive volumes. Therefore, it is desirable to apply the material accurately along a predetermined path within a required cycle time with a predetermined volume and dispersal pattern to provide correct bonding or sealing for the particular application.
The present invention is mountable on the end of a robot arm for applying adhesives and sealers in a swirling pattern to various automotive body parts, by way of example and not limitation, primarily for use in applications known as hem-flange bonding and seam sealing. Applying materials in a wide swirl pattern, as opposed to a single bead form, has certain advantages in the assembly process. The present invention includes a two-pivot bearing; one of which can be positioned off center in a rotating orbital housing, thus achieving an orbiting tip. Rotating power is provided by separate remote in-line or side-mounted motor of an electric, air, or hydraulic type. The present invention permits the ability to increase speed ranges of the orbiting tip by changing a pulley size.
In one embodiment, the entire valve is orbited, while in another embodiment, the valve is remotely mounted and only the nozzle and tip are orbiting. The remote valve version is preferable due to decreased weight, and reduced vibration. The present invention permits the capability to electronically reposition the tip offset during a bead application cycle without stopping. Repositioning the tip offset during a bead application cycle affects a programmable change in the swirl pattern width. By allowing programmable changes in the predetermined application pattern, the same tool can be used for streaming applications, where the motor is stopped, thereby stopping the swirling action, and the materials are streamed or squirted in a single uniform bead along a predetermined path of a part surface, by way of example and not limitation, such as doors, hoods, or other automotive body panels. Presently, orbiting or swirling applicators are unable to accurately predict where the offset tool tip is pointing when the motor is stopped, and therefore the material stream does not consistently hit the target path as the tool tracks around the part surface. The present invention moves the orbital bearing to a null or centered position thereby centering the tip along the tool center line in a predictable and repeatable manner.
In another embodiment, a nozzle design is provided with a tip seal shut-off. The tip seal shut-off nozzle provides instantaneous cut-off of the material stream right at the tip of the nozzle. The present invention in each of the embodiments can be used for dispensing both single and plural component materials. In a plural component material configuration, an in-line disposable mixer nozzle can be provided. Static mixers tend to drip because the fluid shut-off point is upstream from the mixing tube assembly. The mixing tube assembly generally consists of a tube housing, and a length of static elements, typically in one unitary piece, that are loosely contained in the tube. By attaching a valve head to the exit end of the static mixer element, and then pushing the static mixer element and attached valve head, or pulling the element assembly within the tube, an instant shut-off or cut-off of materials at the tip is achieved, i.e. porting or unporting the tip orifice.
The present invention can be used for applying materials in a swirled pattern, or in a direct stream. The pattern generating device can be powered by any suitable motor including electric, air, or hydraulic type of motors. The present invention provides for variable orbit speed, and preferably it is programmable to provide the variable orbit speed required for different application cycles, or during the same application cycle. The variable orbit speed can be synchronized with robot commands as required for specific application cycles. The orbit generating device can be powered by a direct drive, or by an off-set drive configuration. The present invention permits automatically changing from a predetermined swirl pattern to a predetermined null or centered position for streaming application portions of a cycle on the fly (without stopping) via programmed robot command that stops the motor and tool rotation.
The present invention has applications in the hem-flanging process, and also in the seam sealing and sound deadner process commonly used in automated automobile assembly. The ability of the present invention to turn in a circular motion without winding up the material hoses and control lines, make the present invention suitable for other applications including for example, coating the interior of a conduit such as large pipes. In such an application, the adhesive head can be replaced with a spray head on a boom for painting conduit interiors. The swirl diameter is controlled by the degree of orbit ball off-set from the center line. The degree of off-set of the orbit ball can approach up to a maximum of approximately 90xc2x0; however, the maximum degree of off-set of the orbit ball depends on the construction of the orbit housing selected for the particular application. The diameter of the swirl pattern is also dependent on the distance between the orbiting tip and the surface of the part. The swirl diameter and swirl pitch (frequency of loops per inch) is a factor of orbiting speed, to speed along a given path (surface speed) and the distance between the tip/nozzle and the part surface. The orbital off-set adjustment can be accomplished with a rotatable element having an angular bore, where the degree of off-set can be varied by moving the angular bore element or housing forward and aft along a center line of rotation. The angular bore element or housing can be moved manually for changing the orbit angle, or can be moved automatically by, for example a ball screw drive moving the housing fore and aft along the center line of rotation. A ball can be received within the angular bore element or housing for sliding movement within the angled bore to change the radial distance of off-set from the center line of rotation from a zero or null, centered position to a maximum position providing for the maximum radius of circular sweep driven by the angled bore or slot through the element or housing. The rotational circular sweep movement imparted by the ball disposed within the angled slot provides for changing the radius of sweep by moving the angled bore housing with respect to the ball, or by moving the ball with respect to the angled bore housing to change the radius of sweep with respect to the center line from a zero or null, centered position to a maximum value for the radius of sweep. Alternatively, the orbiting ball can be mounted in a moveable plate encased within a rotatable orbit housing, where the movable plate can be disposed at an on-center, zero, null, or off-centered position up to a maximum radial distance value spaced from the center line of rotation.
The applicator tool according to the present invention can be jacketed, or ported, for fluid temperature control purposes. The beads or swirls of material dispensed by the applicator tool can be applied to flat, vertical, and overhead surfaces. The applicator tool can be used with single and plural component materials. The materials to be dispensed are supplied by various pumps and fluid metering systems known to those skilled in the art. Dispense heads according to the present invention can incorporate streaming tip style nozzles with single, or multiple round, or slotted type orifices, to create a multitude of bead or stream patterns.
In one configuration, the material valve or valves can be mounted in line with the circular sweeping element. Alternatively, the material valve or valves can be mounted remote from the circular sweep element to reduce the weight of the orbiting object and the resultant vibration. Remote mounting of the material valve or valves is preferable for high-speed applications. Orbiting speeds for a hem-flange application are expected to be in the range of approximately 5,000 revolutions per minute. Orbiting speeds for a seam sealer application are expected to be in a range of up to 24,000 revolutions per minute. High speeds can create high bearing surface speeds and heat. The bearings of the present invention are large enough to provide sufficient room to introduce lubrication and cooling techniques as required, such as fins, fluids, or the like, and are enclosed in an encasement that is free to align itself with a center line of rotation.
Another aspect of the present invention is a tip seal valve shut-off feature. The tip seal valve shut-off feature provides instant start and stop of beads, thereby eliminating material trails or tails. The quick on-off response time is desirable at high robot travel speeds. The quick on-off response time can apply stitches of material spaced from one another along a predetermined path of travel. The tip seal valve shut-off preferably is mounted to, or integrally formed with, a static mixer element adjacent the exit end and movable into contact with a tapered portion of the discharge tip of the applicator tool. The static mixer element and connected valve head can be moved longitudinally within the housing between a valve open and a valve closed position to provide the shut-off feature.
Another aspect of the present invention is a shield feature. The shield provides an inexpensive and easily installed method of preventing material from being directed away from the workpiece. The shield can be made of a disposable material such as plastic or paper so that cleaning of the shield is unnecessary. The shield can be connected to the orbital applicator tool with an O ring or a strap. The shield includes an opening to allow connection of the inlet port to the applicator tool.